1. Field of the Invention
The field of the invention is computer terminals, and particularly, terminals which include a keyboard for entering information into a digital system and a display for visually displaying the information to an operator.
2. Description of the Prior Art
A general purpose computer terminal of the type well known in the art typically has a data link for receiving data from a computer, a cathode ray tube (CRT) display unit for visually displaying the data to an operator, and a keyboard for manually entering data into the system. The keyboard is usually general purpose in construction, containing standard typewriter keys and perhaps a separate numeric keyboard.
In recent years microprocessors have been employed to carry out the functions of driving the CRT, monitoring the keyboard and controlling communications through the data link. In such microprocessor-based terminals, the microprocessor may be programmed for special functions which allow the terminal to perform limited data processing or word processing functions. Similar to the devices disclosed in U.S. Pat. Nos. 4,028,538 and 3,971,925 such "smart" terminals can be programmed by the operator, using magnetic tape cartridges or modules containing read-only memories, to perform special functions. Commands can then be entered through the keyboard to carry out these special functions. When a general purpose keyboard is employed such commands are directed by selecting one or more keys marked with the standard keyboard characters and this places a burden on the operator to learn a code for these commands. To overcome this problem, some manufacturers provide blank function keys on the keyboard to which the operator can attach symbols which represent the commands, and others, as illustrated in U.S. Pat. Nos. 3,971,925 and 4,156,928 provide separate keyboard modules.